1. Preheat oven to 350 degrees F. Cut each square of pastry into 4 equal size pieces (I trimmed mine just a little). Spread a couple tablespoons of Nutella spread onto the center of each pastry leaving 1/2 inch border around edges. Top each with about 12-15 mini marshmallows and fold over to form a little triangle. Crimp edges firmly with the tines of a fork. Brush with egg white wash then sprinkle with granulated sugar. Bake for 22-25 minutes or until pastry just turns golden. Remove and let cool for 5 minutes, sprinkle with powdered sugar then dig in!